Method of forming phase change material layer using Ge(II) source, and method of fabricating phase change memory device

ABSTRACT

In one aspect, a method of forming a phase change material layer is provided. The method includes supplying a reaction gas including the composition of Formula 1 into a reaction chamber, supplying a first source which includes Ge(II) into the reaction chamber, and supplying a second source into the reaction chamber. Formula 1 is NR 1 R 2 R 3 , where R 1 , R 2  and R 3  are each independently at least one selected from the group consisting of H, CH 3 , C 2 H 5 , C 3 H 7 , C 4 H 9 , Si(CH 3 ) 3 , NH 2 , NH(CH 3 ), N(CH 3 ) 2 , NH(C 2 H 5 ) and N(C 2 H 5 ) 2 .

PRIORITY CLAIM

This application is a continuation-in-part of and claims priority toU.S. patent application Ser. No. 13/429,546, filed Mar. 26, 2012, whichis a continuation of U.S. patent application Ser. No. 12/248,964, filedOct. 10, 2008, now U.S. Pat. No. 8,142,846, which claims priority toKorean Patent Application No. 10-2007-0102585, filed Oct. 11, 2007, inthe Korean Intellectual Property Office, the disclosure of each of whichis incorporated herein in its entirety by reference.

SUMMARY

The present disclosure generally relates to methods of forming a phasechange material layer using a Ge(II) source, and to methods offabricating a phase change memory device.

Chalcogenide is responsive to temperature conditions so as to be stablytransformed between crystalline and amorphous states. The crystallinestate has a lower specific resistance than the amorphous state, and thisphase change property can be utilized to store data. A phase changerandom access memory (PRAM) is one example of a memory device whichutilizes the phase change characteristics of chalcogenide to store data.

Each unit memory cell of a PRAM generally includes an access device anda phase change resistor which may, for example, be electricallyconnected between a bit line and a word line of the PRAM. The phasechange resistor is a variable resistor and generally includes a phasechange material film disposed between a lower electrode and an upperelectrode. Typically, the access device is electrically connected to thelower electrode.

FIG. 1 illustrates temperature conditions applied to the phase changeresistor during “set” and “reset” programming operations. Setprogramming refers to the process of placing the phase change resistorin its crystalline state, whereas reset programming refers to placingthe phase change resistor in its amorphous state. It should be notedthat the terms “crystalline state” and “amorphous state” are relativeterms. That is, the phase change resistor need not be fully crystallinein the crystalline state, and the phase change resistor need not befully amorphous in the amorphous state.

As shown in FIG. 1, set programming entails heating of the phase changematerial of the phase change resistor at a temperature which fallsbetween a crystallization temperature Tx and a melting point temperatureTm, followed by cooling. Reset programming entails heating the phasechange material to the melting point temperature Tm, also followed bycooling. As shown in the figure, the reset programming heat treatment iscarried out for a relative short period of time when compared to that ofthe set programming. Also, the cooling rate in the reset programming maybe more rapid than that of the set programming.

The heat treatment itself is achieved by controlling a write currentthrough the phase change resistor to create joule heating conditionswhich result in temperature profiles that mirror those illustrated inFIG. 1. As a write current flows through the lower electrode and theswitching device of the unit memory cell, joule heat is generated at aboundary surface between the lower electrode and the phase changematerial film. The joule heating induced temperature of the phase changematerial film is dependent upon the magnitude and duration of the writecurrent.

As mentioned above, the present disclosure generally relates to methodsof forming a phase change material layer using a Ge(II) source andmethods of fabricating a phase change memory device.

According to an aspect of the present disclosure, a method of forming aphase change material layer is provided. The method includes supplying areaction gas including the composition of Formula 1 into a reactionchamber, supplying a first source which includes Ge(II) into thereaction chamber, and supplying a second source into the reactionchamber. Formula 1 is NR₁R₂R₃, where R₁, R₂ and R₃ are eachindependently at least one selected from the group consisting of H, CH₃,C₂H₅, C₃H₇, C₄H₉, Si(CH₃)₃, NH₂, NH(CH₃), N(CH₃)₂, NH(C₂H₅) andN(C₂H₅)₂.

According to another aspect of the present disclosure, a method offorming a phase change material layer is provided. The method includesupplying a first source including Ge(II) into a reaction chamber, andsupplying a second source into the reaction chamber.

According to still another aspect of the present disclosure, a method offabricating a phase change memory device is provided. The methodincludes loading a substrate including a lower electrode in a reactionchamber, forming a Ge-containing phase change material layer on thelower electrode by supplying a reaction gas including the composition ofFormula 1, a first source including Ge(II), and a second source into thereaction chamber in which the substrate is loaded, and forming an upperelectrode on the phase change material layer. Formula 1 is NR₁R₂R₃,where R₁, R₂ and R₃ are each independently at least one selected fromthe group consisting of H, CH₃, C₂H₅, C₃H₇, C₄H₉, Si(CH₃)₃, NH₂,NH(CH₃), N(CH₃)₂, NH(C₂H₅) and N(C₂H₅)₂.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects and features will become readily apparentfrom the detailed description that follows, with reference to theaccompanying drawings, in which:

FIG. 1 is a graph illustrating a method of performing a set or resetprogramming for a phase change resistor;

FIG. 2 is a flow chart of a method of forming a Ge-containing phasechange material layer according to an exemplary embodiment;

FIG. 3 is a gas pulsing diagram for use in describing the formation of aGe—Sb—Te layer using chemical vapor deposition according to an exemplaryembodiment;

FIG. 4 is a gas pulsing diagram for use in describing the formation of aGe—Sb—Te layer using atomic layer deposition according to an exemplaryembodiment;

FIGS. 5A and 5B are cross-sectional views of phase change memory devicesprepared according to a method of fabricating a phase change memorydevice according to an exemplary embodiment;

FIGS. 6A, 6B and 6C are cross-sectional views of phase change memorydevices prepared according to a method of fabricating a phase changememory device according to another exemplary embodiment;

FIGS. 7A and 7B are photo images illustrating a phase change materiallayer formed according to an Experimental Example 2;

FIGS. 8A and 8B are photos illustrating a phase change material layerformed according to an Experimental Example 3;

FIGS. 9A and 9B are photos illustrating a phase change material layerformed according to an Experimental Example 4; and

FIG. 10 is a pulsing diagram for describing the formation of a Ge—Sb—Telayer according to certain exemplary embodiments.

DETAILED DESCRIPTION OF EMBODIMENTS

The present disclosure will now be described more fully with referenceto the accompanying drawings, in which exemplary embodiments are shown.The invention may, however, be embodied in many different forms andshould not be construed as being limited to the embodiments set forthherein. In the drawings, the relative thicknesses of layers and regionsare not necessarily drawn to scale and are exaggerated for clarity. Toavoid redundancy in the disclosure, like reference numerals denote thesame or similar elements throughout the drawings.

It will be understood that when an element is referred to as being“connected” or “coupled” to or “on” another element, it can be directlyconnected or coupled to or on the other element or intervening elementsmay be present. In contrast, when an element is referred to as being“directly connected” or “directly coupled” to another element, there areno intervening elements present. As used herein, the term “and/or”includes any and all combinations of one or more of the associatedlisted items and may be abbreviated as “/”.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. Unless indicated otherwise, these terms areonly used to distinguish one element from another. For example, a firstchip could be termed a second chip, and, similarly, a second chip couldbe termed a first chip without departing from the teachings of thedisclosure.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

Embodiments described herein will be described referring to plan viewsand/or cross-sectional views by way of ideal schematic views.Accordingly, the exemplary views may be modified depending onmanufacturing technologies and/or tolerances. Therefore, the disclosedembodiments are not limited to those shown in the views, but includemodifications in configuration formed on the basis of manufacturingprocesses. Therefore, regions exemplified in figures have schematicproperties, and shapes of regions shown in figures exemplify specificshapes of regions of elements, and the specific properties and shapes donot limit aspects of the invention.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element's or feature's relationship to another element(s)or feature(s) as illustrated in the figures. It will be understood thatthe spatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. It willbe further understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and/orthe present application, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

FIG. 2 is a flow chart illustrating a method of forming a phase changematerial layer according to an exemplary embodiment.

Referring to FIG. 2, a substrate is loaded into a reaction chamber(S10). The substrate may include a semiconductor material or film at asurface thereof. Examples of the semiconductor material or film includeSi and/or SiC. In addition, or alternatively, the substrate may includea dielectric and/or conductive material or film at a surface thereof.Examples of the dielectric material or film include silicon oxide,titanium oxide, aluminum oxide (Al₂O₃), zirconium oxide, and/or hafniumoxide. Examples of the conductive material or film include Ti, TiN, Al,Ta, TaN, and/or TiAlN.

The reaction chamber may, for example, be a cold wall type reactionchamber or a hot wall type reaction chamber. Generally, a cold wall typereaction chamber is capable of processing a single substrate at a time,and includes a substrate stage having heating wires and a shower headlocated on the substrate stage. On the other hand, the hot wall typereaction chamber includes heating wires in a wall thereof, such thatmultiple substrates can be vertically stacked within the chamber andbatched processed at the same time. In any event, the embodiment is notlimited to any particular type of reaction chamber.

Referring again to the example of FIG. 2, a reaction gas which includesa composition represented by Formula 1 is supplied in to the reactionchamber (S20).NR₁R₂R₃  Formula 1wherein R₁, R₂ and R₃ are each independently H, CH₃, C₂H₅, C₃H₇, C₄H₉,Si(CH₃)₃, NH₂, NH(CH₃), N(CH₃)₂, NH(C₂H₅) or N(C₂H₅)₂.

In the preceding paragraph and through this disclosure, the word“independently” means that any two or more of R₁, R₂ and R₃ can be thesame as each other, or R₁, R₂ and R₃ can all be different from eachother.

The representation of Formula 1 includes non-ring systems, and ringsystems in which two or more of R₁, R₂ and R₃ are bonded to each other.In other words, according to Formula 1, two or more of R₁, R₂ and R₃ mayor may not be bonded to eachother.

As one particular example, the reaction gas is an NH₂ gas. Otherspecific examples of the reaction gas any one or more of ammonia,primary amine and hydrazine.

Referring again to FIG. 2, a Ge(II) source is supplied as a first sourceinto the reaction chamber (S30). Here, “II” denotes an oxidation stateof the Ge is +2. The Ge(II) can be supplied before and/or after and/orat the same time the reaction gas is supplied into the reaction chamber.

The Ge(II) source may, for example, be supplied together with a carriergas. Examples of the carrier gas include an inert gas such as argon(Ar), helium (He) or nitrogen (N₂). As another example, the Ge(II)source may be supplied into the reaction chamber by being dissolved in asolvent and rapidly gasified in a gasifier.

Examples of Ge(II) source include an amide ligand, a phosphanido ligand,an alkoxide ligand or a thiolate ligand.

In the case where the Ge(II) source includes an amide ligand and/or aphosphanido ligand, the Ge(II) source may include a compositionrepresented by Formula 2 below:R₁R₂X₁—Ge—X₂R₃R₄  Formula 2wherein X₁ and X₂ are each independently at least one of N and P, andwherein R₁, R₂, R₃ and R₄ are each independently at least one (i.e., oneor a combination of two or more) selected from the group consisting of(a) a hydrogen atom, (b) a C₁-C₁₀ alkyl group, (c) a C₁-C₁₀ alkyl group,where CH₃ is substituted with an imine group, an amine group, an alkoxygroup or a ketone group, (d) a C₁-C₁₀ alkyl group, where CH₃ issubstituted with an imine group, an amine group, an alkoxy group or aketone group, and where N of the imine group, N of the amine group, O ofthe alkoxy group or O of the ketone group is coordinated with Ge, (e) aC₂-C₁₂ olefinic group, (f) a C₃-C₁₂ olefinic group, where CH₃ issubstituted with an imine group, an amine group, an alkoxy group or aketone group, (g) a C₃-C₁₂ olefinic group, where CH₃ is substituted withan imine group, an amine group, an alkoxy group or a ketone group, andwhere N of the imine group, N of the amine group, O of the alkoxy groupor O of the ketone group is coordinated with Ge, (h) a C₂-C₁₃ acetylenicgroup, (i) an allenic group (CHCCH₂), (j) a cyano group (CN), (k) a NCXgroup, wherein X is O, S, Se or Te, (l) an azide ligand (N₃), (m) anamide ligand (NR₅R₆, where R₅ and R₆ are each independently a hydrogenatom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenicgroup or an allenic group), and (n) SiR₇R₈R₉, where R₇, R₈ and R₉ areeach independently a hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂olefinic group, a C₂-C₁₃ acetylenic group or an allenic group.

The representation of Formula 2 includes non-ring systems, andring-systems in which two or more of R₁, R₂, R₃ and R₄ are bonded toeach other. In other words, according to Formula 2, two or more of R₁,R₂, R₃ and R₄ may or may not be bonded to each other.

In the case where the Ge(II) source includes an alkoxide ligand and/or athiolate ligand, the Ge(II) source may include a composition representedby Formula 3 below:R₁Y₁—Ge—Y₂R₂  Formula 3wherein Y₁ and Y₂ are each independently at least one of O and S, andwherein R₁ and R₂ are each independently at least one selected from thegroup consisting of (a) a hydrogen atom, (b) a C₁-C₁₀ alkyl group, (c) aC₁-C₁₀ alkyl group, where CH₃ is substituted with an imine group, anamine group, an alkoxy group or a ketone group, (d) a C₁-C₁₀ alkylgroup, where CH₃ is substituted with an imine group, an amine group, analkoxy group or a ketone group, and where N of the imine group, N of theamine group, O of the alkoxy group or O of the ketone group iscoordinated with Ge, (e) a C₂-C₁₂ olefinic group, (f) a C₃-C₁₂ olefinicgroup, where CH₃ is substituted with an imine group, an amine group, analkoxy group or a ketone group, (g) a C₃-C₁₂ olefinic group, where CH₃is substituted with an imine group, an amine group, an alkoxy group or aketone group, and where N of the imine group, N of the amine group, O ofthe alkoxy group or O of the ketone group is coordinated with Ge, (h) aC₂-C₁₃ acetylenic group, (i) an allenic group (CHCCH₂), (j) a cyanogroup (CN), (k) a NCX group, where X is O, S, Se or Te, (l) an azideligand (N₃), (m) an amide ligand (NR₃R₄, where R₃ and R₄ are eachindependently a hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinicgroup, a C₂-C₁₃ acetylenic group or an allenic group), and (n) SiR₅R₆R₇,where R₅, R₆ and R₇ are each independently a hydrogen atom, a C₁-C₁₀alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenic group or anallenic group.

The representation of Formula 2 includes non-ring systems, and ringsystems in which R₁ and R₂ are bonded to each other. In other words,according to Formula 3, R₁ and R₂ may or may not be bonded to eachother.

In the case where the Ge(II) source includes one of the amide ligand andthe phosphanido ligand; and one of the alkoxide ligand and the thiolateligand, the Ge(II) may include a composition represented by Formula 4below:R₁R₂X—Ge—YR₃  Formula 4wherein X is at least one of N and P, wherein Y is at least one of O andS, and wherein R₁, R₂ and R₃ are each independently at least oneselected from the group consisting of (a) a hydrogen atom, (b) a C₁-C₁₀alkyl group, (c) a C₁-C₁₀ alkyl group, where CH₃ is substituted with animine group, an amine group, an alkoxy group or a ketone group, (d) aC₁-C₁₀ alkyl group, where CH₃ is substituted with an imine group, anamine group, an alkoxy group or a ketone group, and where N of the iminegroup, N of the amine group, O of the alkoxy group or O of the ketonegroup is coordinated with Ge, (e) a C₂-C₁₂ olefinic group, (f) a C₃-C₁₂olefinic group, where CH₃ is substituted with an imine group, an aminegroup, an alkoxy group or a ketone group, and where N of the iminegroup, N of the amine group, O of the alkoxy group or O of the ketonegroup is coordinated with Ge, (g) a C₂-C₁₃ acetylenic group, (h) anallenic group (CHCCH₂), (i) a cyano group (CN), (j) a NCX group, where Xis O, S, Se or Te, (k) an azide ligand (N₃), (l) an amide ligand (NR₄R₅,where R₄ and R₅ are each independently a hydrogen atom, a C₁-C₁₀ alkylgroup, a C₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenic group or an allenicgroup), and (m) SiR₆R₇R₈, where R₆, R₇ and R₈ are each independently ahydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃acetylenic group or an allenic group.

The representation of Formula 4 includes non-ring systems, and ringsystems in which two or more of R₁, R₂ and R₃ are bonded to each other.In other words, according to Formula 4, two or more of R₁, R₂ and R₃ mayor may not be bonded to eachother.

Examples of Ge(II) source compositions represented by Formula 2 arepresented below as Formulae 5 to 11:

wherein X₁ and X₂ are each independently N or P, and wherein R₁, R₂, R₃and R₄ are each independently one selected from the group consisting ofa hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃acetylenic group and an allenic group;

wherein X₁ and X₂ are each independently N or P, and wherein R₁ and R₂are each independently one selected from the group consisting of ahydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃acetylenic group and an allenic group;

wherein X₁, X₂, X₃ and X₄ are each independently N or P, and wherein R₁,R₂, R₃, R₄, R₅ and R₆ are each independently one selected from the groupconsisting of a hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinicgroup, a C₂-C₁₃ acetylenic group and an allenic group;

wherein X₁ and X₂ are each independently N or P, wherein Y₁ and Y₂ areeach independently O or S, and wherein R₁, R₂, R₃, R₄, R₅, R₆, R₇ and R₈are each independently one selected from the group consisting of ahydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃acetylenic group and an allenic group;

wherein X₁, X₂, X₃ and X₄ are each independently N or P, and wherein R₁,R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉ and R₁₀ are each independently oneselected from the group consisting of a hydrogen atom, a C₁-C₁₀ alkylgroup, a C₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenic group and an allenicgroup;

wherein X₁, X₂, X₃ and X₄ are each independently N or P, and wherein R₁,R₂, R₃, R₄, R₅ and R₆ are each independently one selected from the groupconsisting of a hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinicgroup, a C₂-C₁₃ acetylenic group and an allenic group; and

wherein X₁ and X₂ are each independently N or P, wherein Y₁ and Y₂ areeach independently O or S, and wherein R₁, R₂, R₃ and R₄ are eachindependently one selected from the group consisting of a hydrogen atom,a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenic groupand an allenic group.

Examples of Ge(II) source compositions represented by Formula 3 arepresented below as Formulae 12 to 16:

wherein Y₁ and Y₂ are each independently O or S, and wherein R₁ and R₂are each independently one selected from the group consisting of ahydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃acetylenic group and an allenic group;

wherein Y₁ and Y₂ are each independently O or S, and wherein R₁ and R₂are each independently one selected from the group consisting of ahydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃acetylenic group and an allenic group;

wherein Y₁, Y₂, Y₃ and Y₄ are each independently O or S, and wherein R₁,R₂, R₃, R₄, R₅ and R₆ are each independently one selected from the groupconsisting of a hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinicgroup, a C₂-C₁₃ acetylenic group and an allenic group;

wherein X₁ and X₂ are each independently N or P, wherein Y₁ and Y₂ areeach independently O or S, and wherein R₁, R₂, R₃ and R₄ are eachindependently selected from the group consisting of a hydrogen atom, aC₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenic groupand an allenic group; and

wherein Y₁, Y₂, Y₃ and Y₄ are each independently O or S, and wherein R₁and R₂ are each independently one selected from the group consisting ofa hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃acetylenic group and an allenic group.

An example of a Ge(II) source composition represented by Formula 4 ispresented below as Formulae Formula 17:

wherein X is N or P, wherein Y is O or S, and wherein R₁, R₂ and R₃ areeach independently one selected from the group consisting of a hydrogenatom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenicgroup and an allenic group.

When compared to a Ge(IV) source, the Ge(II) sources described aboveexhibit fewer ligands and a weaker covalent bond property between the Geand the ligands. According, steric hindrance caused by ligands isrelatively weak in the Ge(II) source. Even when the number of ligands ofthe Ge(II) source and Ge(IV) source is the same, a dative bond among theGe-ligand bonds of the Ge(II) source may be relatively easilydisconnected by heat of the reaction chamber, and thus the Ge(II) sourceis transformed to a structure with low steric hindrance due to thereduced number of the ligands linked to Ge. Accordingly, the Ge(II)source exhibits improved reactivity when compared to the Ge(IV) source,and thus a temperature required to form the phase change material layercan be reduced.

In particular, for example, the Ge(II) source represented by Formulae 5,6, 12, 13 and 17 has two atoms linked to Ge, and thus steric hindranceis relatively low. The Ge(II) source represented by Formulae 7, 8, 9 and14 has four atoms linked to Ge, but the steric hindrance is stillrelatively low since the top and bottom of the Ge are sterically openedsince two ligands of both sides of Ge are almost in the same plane. TheGe(II) source represented by Formulae 10, 11, 15 and 16 also has fouratoms linked to Ge, but the steric hindrance is also relatively lowsince the Ge(II) source is transformed to a structure having two atomslinked to Ge because a dative bond among the Ge-ligand bonds is easilydisconnected by heat of the reaction chamber as shown in ReactionSchemes 1 to 4.

In Reaction Scheme 1, X₁, X₂, X₃ and X₄ are each independently N or P,and R₁, R₂, R₃, R₄, R₅ and R₆ are each independently a hydrogen atom, aC₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenic groupor an allenic group.

In Reaction Scheme 2, X₁ and X₂ are each independently N or P, Y₁ and Y₂are each independently O or S, and R₁, R₂, R₃ and R₄ are eachindependently a hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinicgroup, a C₂-C₁₃ acetylenic group or an allenic group.

In Reaction Scheme 3, X₁ and X₂ are each independently N or P, Y₁ and Y₂are each independently O or S, and R₁, R₂, R₃ and R₄ are eachindependently a hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinicgroup, a C₂-C₁₃ acetylenic group or an allenic group.

In Reaction Scheme 4, Y₁, Y₂, Y₃ and Y₄ are each independently O or S,and R₁ and R₂ are each independently a hydrogen atom, a C₁-C₁₀ alkylgroup, a C₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenic group or an allenicgroup.

Returning once again to FIG. 2, a second source is supplied into thereaction chamber (S40). The second source may be supplied before orafter the reaction gas and/or the Ge(II) source is supplied, orsimultaneously with the reaction gas and the Ge(II) source. As a result,a Ge-containing phase change material layer is formed on the substrate(S50).

The second source may also be supplied into the reaction chamber with acarrier gas. Examples of the carrier gas include an inert gas such asargon (Ar), helium (He) or nitrogen (N₂). As an alternative example, thesecond source may be supplied into the reaction chamber by beingdissolved in a solvent and rapidly gasified in a gasifier.

Examples of the second source include one or more of a Te source, a Sbsource, a Bi source, an As source, a Sn source, an O source, an Ausource, a Pd source, a Se source, a Ti source and a S source. Theresultant Ge-containing phase change material layer may, for example, beformed as a Ge—Sb—Te layer, Ge—Bi—Te layer, Ge—Sb layer, Ge—Te—As layer,Ge—Te—Sn layer, Ge—Te layer, Ge—Te—Sn—O layer, Ge—Te—Sn—Au layer,Ge—Te—Sn—Pd layer, Ge—Te—Se layer, Ge—Te—Ti layer, (Ge, Sn)—Sb—Te layer,Ge—Sb—(Se, Te) layer or Ge—Sb—Te—S layer. The Ge-containing phase changematerial layer may also include one or more impurities such as N, O, Bi,Sn, B, Si or a combination thereof.

For example, when a Te source and/or a Sb source is supplied as thesecond source, the Ge-containing phase change material layer formed onthe substrate may be Ge—Sb—Te layer, Ge—Te layer or Ge—Sb layer.Specific examples of the Te source include Te(CH₃)₂, Te(C₂H₅)₂,Te(n-C₃H₇)₂, Te(i-C₃H₇)₂, Te(t-C₄H₉)₂, Te(i-C₄H₉)₂, Te(CH═CH₂)₂,Te(CH₂CH═CH₂)₂, or Te[N(Si(CH₃)₃)₂]₂. Specific examples of the Sb sourceinclude Sb(CH₃)₃, Sb(C₂H₅)₃, Sb(i-C₃H₇)₃, Sb(n-C₃H₇)₃, Sb(i-C₄H₉)₃,Sb(t-C₄H₉)₃, Sb(N(CH₃)₂)₃, Sb(N(CH₃)(C₂H₅))₃, Sb(N(C₂H₅)₂)₃,Sb(N(i-C₃H₇)₂)₃ or Sb[N(Si(CH₃)₃)₂]₃.

The Ge(II) source may react with the reaction gas to form a Ge(II)intermediate in which ligands neighboring the Ge are substituted by thereaction gas. The Ge(II) intermediate may include two NR₁R₂ ligands,wherein R₁ and R₂ are each independently H, CH₃, C₂H₅, C₃H₇, C₄H₉,Si(CH₃)₃, NH₂, NH(CH₃), N(CH₃)₂, NH(C₂H₅) or N(C₂H₅)₂ around Ge. Here,since reactivity between the Ge(II) source and the reaction gas isimproved when compared to the reactivity between the Ge(IV) source andthe reaction gas, the reaction temperature may be reduced. For example,the Ge(II) source represented by Formula 5 reacts with ammonia to form aGe(II) intermediate as shown in Reaction Scheme 5 below.

In Reaction Scheme 5, X₁ and X₂ are each independently N or P, and R₁,R₂, R₃ and R₄ are each independently a hydrogen atom, a C₁-C₁₀ alkylgroup, a C₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenic group or an allenicgroup.

The Ge(II) intermediate may react with the second source to form aGe-containing phase change material layer. For example, the Ge(II)intermediate prepared according to Reaction Scheme 5 reacts with a Tesource to form a phase change material layer as shown in Reaction Scheme6 below.

In Reaction Scheme 6, R′ is CH(CH₃)₂.

The Ge(II) intermediate is highly reactive with the second source.Further, similar to the Ge(II) source, the Ge(II) intermediate exhibitslow steric hindrance by ligands. As a result, the reaction temperaturemay be further reduced, and the deposition temperature of theGe-containing phase change material layer may be reduced. For example,the deposition temperature of the Ge-containing phase change materiallayer may be less than 300° C., and further, may be 200° C. or less. Thegrain size of a phase change material layer deposited at such a lowtemperature is smaller than that of a phase change material layerdeposited at a higher temperature. A smaller grain size improves stepcoverage, which allows a conformal phase change material layer to beformed on the side wall of a contact hole or trench without blocking thehole or trench inlet, thereby avoid the formation of voids within thehole or trench.

The Ge-containing phase change material layer may, for example, beformed using chemical vapor deposition (CVD) or atomic layer deposition(ALD).

FIG. 3 is an example of a gas pulsing diagram in the case where aGe—Sb—Te layer is formed using chemical vapor deposition.

Referring to FIG. 3, a Ge(II) source, a Sb source and a Te source aresimultaneously supplied into a reaction chamber while a carrier gas anda reaction gas are supplied into the reaction chamber. The firstreaction gas may be NR₁R₂R₃, wherein R₁, R₂ and R₃ are eachindependently H, CH₃, C₂H₅, C₃H₇, C₄H₉, Si(CH₃)₃, NH₂, NH(CH₃), N(CH₃)₂,NH(C₂H₅) or N(C₂H₅)₂. As particular examples, the reaction gas may beammonia, primary amine or hydrazine. The carrier gas may, for example,be an inert gas such as argon (Ar), helium (He) or nitrogen (N₂). TheGe(II) source may be a Ge(II) source as previous described, and mayinclude, for example, an amide ligand, a phosphanido ligand, an alkoxideligand or a thiolate ligand. The Ge(II) source may react with thereaction gas to form a Ge(II) intermediate in which ligands neighboringGe are substituted with ligands associated with the reaction gas, andthe Ge(II) intermediate may react with the Te source to form GeTe. Inaddition, the Te source reacts with the Sb source to form Sb₂Te₃. TheGeTe and the Sb₂Te₃ can form a Ge—Sb—Te layer having Ge₂Sb₂Te₅composition. Here, since reactivity between the Ge(II) source and thereaction gas and reactivity between the Ge(II) intermediate and the Tesource are improved, a temperature required to deposit GeTe may bereduced. Each of the Ge(II) source, the Sb source and the Te source maybe injected at 10 to 1000 sccm for 1 to 1000 seconds. The time forinjecting the Ge(II) source, the Sb source and the Te source into thereaction chamber may be defined as deposition time.

FIG. 4 is an example of a gas pulsing diagram in the case where aGe—Sb—Te layer is formed using atomic layer deposition.

Referring to FIG. 4, a Ge(II) source and a Te source are injected to areaction chamber while a first carrier gas and a first reaction gas aresupplied to the reaction chamber for time T1 to form a Ge—Te layer(first operation). The first reaction gas may be NR₁R₂R₃, wherein R₁, R₂and R₃ are each independently H, CH₃, C₂H₅, C₃H₇, C₄H₉, Si(CH₃)₃, NH₂,NH(CH₃), N(CH₃)₂, NH(C₂H₅) or N(C₂H₅)₂. As particular examples, thereaction gas may be ammonia, primary amine or hydrazine. The firstcarrier gas may, for example, include an inert gas such as argon (Ar),helium (He) or nitrogen (N₂). The Ge(II) source may include a Ge(II)source as described previously, and may include amide ligand, aphosphanido ligand, an alkoxide ligand or a thiolate ligand. The Ge(II)source may react with the first reaction gas to form a Ge(II)intermediate in which ligands neighboring Ge are substituted withligands associated with the reaction gas, and the Ge(II) intermediatemay react with the Te source to form GeTe. Here, since reactivitybetween the Ge(II) source and the first reaction gas and reactivitybetween the Ge(II) intermediate and the Te source are improved, atemperature required to deposit GeTe may be reduced.

Then, physically adsorbed Ge(II) source and Te source; and unreactedGe(II) source and Te source are removed by supplying the first carriergas and the first reaction gas to the reaction chamber while the supplyof the sources is suspended for time T2 (second operation).

A Sb source and a Te source are injected to the reaction chamber whilesupplying a second carrier and a second reaction gas to the reactionchamber for time T3 to form a Sb—Te layer, for example, a Sb₂Te₃ layer(third operation). The second reaction gas may independently includehydrogen (H₂), oxygen (O₂), ozone (O₃), water vapor (H₂O), silane(SiH₄), diborane (B₂H₆), hydrazine (N₂H₄), primary amine or ammonia(NH₃), and the second carrier gas may independently include an inert gassuch as argon (Ar), helium (He) or nitrogen (N₂).

Physically adsorbed Sb source and Te source, and unreacted Sb source andTe source are removed by supplying the second carrier gas and the secondreaction gas to the reaction chamber while the supply of the sources issuspended for time T4 (fourth operation).

A unit cycle including the first to fourth operations (T1˜T4) may berepeated to form a Ge—Sb—Te layer, for example, a Ge—Sb—Te layer havingGe₂Sb₂Te₅ composition. Each of the Ge(II) source, the Sb source and theTe source may be injected at 10 to 1000 sccm for 0.1 to 60 seconds.

FIGS. 5A and 5B are cross-sectional views of phase change memory devicesprepared according to a method of fabricating a phase change memorydevice according to an exemplary embodiment.

Referring to FIG. 5A, an isolation layer (not shown) is formed on asubstrate 100 to define an active region. A gate insulating layer 105and a gate conductive layer are sequentially stacked on the activeregion, and the gate conductive layer 110 and the gate insulating layer105 are etched to form a gate electrode 110. Impurities are doped on thesubstrate 100 to a low concentration using the gate electrode 110 as amask to form a low concentration impurity region 101 a neighboring thegate electrode 110 in the substrate 100.

A gate spacer insulating layer is stacked on the substrate 100 on whichthe low concentration impurity region 101 a is formed, and the gatespacer insulating layer is anisotropically etched to form a gate spacer115 on the side wall of the gate electrode 110. Then, impurities aredoped on the substrate 100 to a high concentration using the gateelectrode 110 and the gate spacer 115 as masks to form a highconcentration impurity region 101 b neighboring the gate spacer 115 inthe substrate 100.

The low concentration impurity region 101 a and the high concentrationimpurity region 101 b form source/drain regions. The low concentrationimpurity region 101 a and the high concentration impurity region 101 bof one end of the gate electrode 110 form a source region 102, and thelow concentration impurity region 101 a and the high concentrationimpurity region 101 b of the other end of the gate electrode 110 form adrain region 103. The gate electrode 110, the source region 102 and thedrain region 103 constitute a MOS transistor which functions as anaccess device. However, the access device is not limited to the MOStransistor, and may instead be a diode or a bipolar transistor.

A first interlayer insulating layer 120 is formed on the substrate 100on which the source/drain regions 102 and 103 are formed, and a contactplug 125 passing through the first interlayer insulating layer 120 andconnected to the drain region 103 is formed within the first interlayerinsulating layer 120. The contact plug 125 may, for example, be formedof a tungsten layer.

A lower electrode 135 covering the contact plug 125 is formed on thecontact plug 125. The lower electrode 135 may, for example, be formed ofa titanium nitride layer (TiN), a titanium aluminum nitride layer(TiAlN), a tantalum nitride layer (TaN), a tungsten nitride layer (WN),a molybdenum nitride layer (MoN), a niobium nitride layer (NbN), atitanium silicon nitride layer (TiSiN), a titanium boron nitride layer(TiBN), a zirconium silicon nitride layer (ZrSiN), a tungsten siliconnitride layer (WSiN), a tungsten boron nitride layer (WBN), a zirconiumaluminum nitride layer (ZrAlN), a molybdenum aluminum nitride layer(MoAlN), a tantalum silicon nitride layer (TaSiN), a tantalum aluminumnitride layer (TaAlN), a titanium tungsten layer (TiW), a titaniumaluminum layer (TiAl), a titanium oxynitride layer (TiON), a titaniumaluminum oxynitride layer (TiAlON), a tungsten oxynitride layer (WON) ora tantalum oxynitride layer (TaON).

A mold insulating layer 140 is formed on the lower electrode 135, and avia hole 140 a which exposes a part of the lower electrode 135 is formedwithin the mold insulating layer 140. A hole spacer insulating layer isformed on the substrate on which the via hole 140 a is formed, and thehole spacer insulating layer is anisotropically etched to expose thelower electrode 135 in the via hole 140 a. Thus, a hole spacer 145 isformed on the side wall of the via hole 140 a. Accordingly, an effectivediameter of the via hole 140 a may be less than a resolution limit oflithography due to the hole spacer 145.

Then, a phase change material layer 150 is formed on the substrate onwhich the via hole 140 a is formed. The phase change material layer 150may be a Ge-containing phase change material layer, and formed using themethod of FIG. 2. Thus, the deposition temperature of the phase changematerial layer 150 may be reduced to less than 300° C. Furthermore, thedeposition temperature of the phase change material layer 150 may bereduced to 200° C. The phase change material layer 150 deposited at suchas low temperature has less grain size than a phase change materiallayer deposited at a high temperature. Thus, the phase change materiallayer 150 can fill the via hole 140 a without voids even when theeffective diameter of the via hole 140 a is extremely small.

Referring to FIG. 5B, a phase change material pattern 151 is formed byplanarizing the phase change material layer 150. An upper electrode 160is formed on the phase change material pattern 151. The phase changematerial layer 150 may be planarized using etch back or chemicalmechanical polishing (CMP). As a result, a phase change resistorincluding the lower electrode 135, the upper electrode 160 and the phasechange material pattern 151 interposed between the lower electrode 135and the upper electrode is formed.

FIGS. 6A, 6B and 6C are cross-sectional views of phase change memorydevices prepared according to a method of fabricating a phase changememory device according to another exemplary embodiment. The method ofFIGS. 6A˜6C is similar to that of FIGS. 5A and 5B, and accordingly, toavoid redundancy in the description, a discussion of like aspectsbetween the two methods is omitted below.

Referring to FIG. 6A, a mold insulating layer 140 is formed on the lowerelectrode 135, and a via hole 140 a which exposes a part of the lowerelectrode 135 is formed within the mold insulating layer 140. A phasechange material layer 152 is formed in the via hole 140 a. The phasechange material layer 152 does not fully fill the via hole 140 a, but isformed to conformally cover the side wall of the via hole 140 a. Thephase change material layer 152 may be a Ge-containing phase changematerial layer, and formed using the method of FIG. 2. Thus, thedeposition temperature of the phase change material layer 152 may bereduced to less than 300° C. Furthermore, the deposition temperature ofthe phase change material layer 152 may be reduced to 200° C. The phasechange material layer 152 deposited at such as low temperature has lessgrain size than a phase change material layer deposited at a hightemperature. Thus, the phase change material layer 152 can conformallycover the side wall of the via hole 140 a without blocking the upperportion of the via hole 140 a.

Referring to FIG. 6B, the phase change material layer 152 isanisotropically etched until the lower electrode 135 is exposed to forma phase change material spacer 153 on the side wall of the via hole 140a and to expose the upper surface of the mold insulating layer 140. Abuffer insulating layer 155 is formed on the exposed lower electrode 135and the mold insulating layer 140. The buffer insulating layer 155 isformed to fill the via hole 140 a. In the via hole 140 a, the side wallof the buffer insulating layer 155 is covered by the phase changematerial spacer 153.

The substrate on which the buffer insulating layer 155 is formed isplanarized to expose the upper surface of the phase change materialspacer 153. For example, the substrate may be planarized to the dashedline shown in FIG. 6B.

Referring to FIG. 6C, an upper electrode 160 is formed on the phasechange material spacer 153, the upper surface of which is exposed. Thus,a phase change resistor including the lower electrode 135, the upperelectrode 160 and the phase change material spacer 153 interposedbetween the lower electrode 135 and the upper electrode 160 is formed.The contact area between the phase change material spacer 153 and thelower electrode 135 may be reduced when compared to the phase changematerial pattern described with reference to FIG. 5B. Accordingly, aneffective current density of a writing current applied to the phasechange material spacer 153 may further be increased.

Described next are a number of Experimental Examples (1˜13) andComparative Examples (1˜2).

Experimental Example 1

A substrate was loaded in a reaction chamber. Ar as a carrier gas wassupplied into the reaction chamber at 500 sccm and NH₃ as a reaction gaswas supplied into the reaction chamber at 100 sccm. A Ge(II) sourcerepresented by Formula 18 below was supplied into the reaction chamberat 100 sccm. Simultaneously, Te(CH(CH₃)₂)₂ was supplied into thereaction chamber at 100 sccm to form a GeTe layer on the substrate. Thesupply of the Ge(II) source and the Te(CH(CH₃)₂)₂ was performed for 900seconds. The temperature of a heater of the reaction chamber was set to320° C.

Experimental Example 2

A GeTe layer was formed on the substrate in the same manner as inExperimental Example 1, except that the temperature of a heater of thereaction chamber was set to 280° C.

Experimental Example 3

A GeTe layer was formed on the substrate in the same manner as inExperimental Example 1, except that the temperature of a heater of thereaction chamber was set to 240° C.

Experimental Example 4

A GeTe layer was formed on the substrate in the same manner as inExperimental Example 1, except that the temperature of a heater of thereaction chamber was set to 200° C.

Experimental Example 5

A substrate was loaded in a reaction chamber. Ar as a carrier gas wassupplied into the reaction chamber at 500 sccm and NH₃ as a reaction gaswas supplied into the reaction chamber at 100 sccm. A Ge(II) sourcerepresented by Formula 19 below was supplied into the reaction chamberat 100 sccm. Simultaneously, Te(CH(CH₃)₂)₂ was supplied into thereaction chamber at 100 sccm to form a GeTe layer on the substrate. Thesupply of the Ge(II) source and the Te(CH(CH₃)₂)₂ was performed for 900seconds. The temperature of a heater of the reaction chamber was set to320° C.

Experimental Example 6

A GeTe layer was formed on the substrate in the same manner as inExperimental Example 5, except that the temperature of a heater of thereaction chamber was set to 280° C.

Experimental Example 7

A GeTe layer was formed on the substrate in the same manner as inExperimental Example 5, except that the temperature of a heater of thereaction chamber was set to 240° C.

Experimental Example 8

A substrate was loaded in a reaction chamber. Ar as a carrier gas wassupplied into the reaction chamber at 500 sccm and H₂ as a reaction gaswas supplied into the reaction chamber at 100 sccm. A Ge(II) sourcerepresented by Formula 18 was supplied into the reaction chamber at 100sccm. Simultaneously, Te(CH(CH₃)₂)₂ was supplied into the reactionchamber at 100 sccm to form a GeTe layer on the substrate. The supply ofthe Ge(II) source and the Te(CH(CH₃)₂)₂ was performed for 900 seconds.The temperature of a heater of the reaction chamber was set to 320° C.

Experimental Example 9

A GeTe layer was formed on the substrate in the same manner as inExperimental Example 8, except that the temperature of a heater of thereaction chamber was set to 280° C.

Experimental Example 10

A GeTe layer was formed on the substrate in the same manner as inExperimental Example 8, except that the temperature of a heater of thereaction chamber was set to 240° C.

Experimental Example 11

A substrate was loaded in a reaction chamber. Ar as a carrier gas wassupplied into the reaction chamber at 500 sccm and H₂ as a reaction gaswas supplied into the reaction chamber at 100 sccm. A Ge(II) sourcerepresented by Formula 19 was supplied into the reaction chamber at 100sccm. Simultaneously, Te(CH(CH₃)₂)₂ was supplied into the reactionchamber at 100 sccm to form a GeTe layer on the substrate. The supply ofthe Ge(II) source and the Te(CH(CH₃)₂)₂ was performed for 900 seconds.The temperature of a heater of the reaction chamber was set to 320° C.

Experimental Example 12

A GeTe layer was formed on the substrate in the same manner as inExperimental Example 11, except that the temperature of a heater of thereaction chamber was set to 280° C.

Experimental Example 13

A GeTe layer was formed on the substrate in the same manner as inExperimental Example 11, except that the temperature of a heater of thereaction chamber was set to 240° C.

Comparative Example 1

A substrate was loaded in a reaction chamber. Ar as a carrier gas wassupplied into the reaction chamber at 500 sccm and NH₃ as a reaction gaswas supplied into the reaction chamber at 100 sccm. Ge(N(CH₃)₂)₄ as aGe(IV) source was supplied into the reaction chamber at 100 sccm.Simultaneously, Te(CH(CH₃)₂)₂ was supplied into the reaction chamber at100 sccm to form a GeTe layer on the substrate. The supply of the Ge(IV)source and the Te(CH(CH₃)₂)₂ was performed for 900 seconds. Thetemperature of a heater of the reaction chamber was set to 320° C.

Comparative Example 2

A GeTe layer was formed on the substrate in the same manner as inComparative Example 1, except that the temperature of a heater of thereaction chamber was set to 280° C.

Experimental conditions of Experimental Examples 1 to 13, andComparative Examples 1 and 2, and deposition rates of the resultant GeTelayers are shown in Table 1 below.

TABLE 1 Heater Deposition temperature rate of Reaction in reactionSb₂Te₃ layer Ge source gas chamber (° C.) (Å/min) Experimental Ge(II)source NH₃ 320 12 Example 1 of Formula 18 Experimental 280 10 Example 2Experimental 240 7 Example 3 Experimental 200 3 Example 4 ExperimentalGe(II) source 320 8 Example 5 of Formula 19 Experimental 280 4 Example 6Experimental 240 2 Example 7 Comparative Ge(IV) source 320 DepositedExample 1 Ge(N(CH₃)₂)₄ Comparative 280 Not Example 2 depositedExperimental Ge(II) source H₂ 320 4 Example 8 of Formula 18 Experimental280 0.7 Example 9 Experimental 240 0.1 Example 10 Experimental Ge(II)source 320 3 Example 11 of Formula 19 Experimental 280 0.8 Example 12Experimental 240 0.1 Example 13

Referring to Table 1, when the reaction gas was NH₃, a phase changematerial layer was formed at a temperature less than 300° C., that is,at 280° C., at 240° C., and even at 200° C. using the Ge(II) source ofFormula 18. However, when using the Ge(IV) source, a phase changematerial layer was not formed at a temperature less than 300° C. A phasechange material layer was also be formed at a temperature less than 300°C., that is, at 280° C. and at 240° C. using the Ge(II) source ofFormula 19.

When the reaction gas was H₂, a phase change material layer was formedat a temperature less than 300° C., that is, at 280° C. and at 240° C.using the Ge(II) source of Formula 18. However, the deposition rate ofthe phase change material layer at 280° C. and 240° C. was relativelylow. The same result was obtained when using the Ge(II) source ofFormula 19.

FIGS. 7A and 7B are photographic images of a phase change material layerformed according to Experimental Example 2 (NH₃ reaction gas and 280° C.deposition). FIGS. 8A and 8B are photographic images of a phase changematerial layer formed according to Experimental Example 3 (NH₃ reactiongas and 240° C. deposition). FIGS. 9A and 9B are photographic images ofa phase change material layer formed according to Experimental Example 4(NH₃ reaction gas and 200° C. deposition). Each of the photographicimages provides visual confirmation that the phase change material layerconformally covered the side wall of a contact hole without blocking theentrance to the hole and without creating voids within the hole.

FIG. 10 is a pulsing diagram for describing the formation of a Ge—Sb—Telayer according to certain exemplary embodiments. As shown in FIG. 10,to form a phase change material layer, different substances can beprovided to a reaction chamber at different times within repeatedcycles. For example, a reaction gas, a first source, and a second sourcemay be supplied to the reaction chamber. In certain embodiments, thefirst source is a Ge source, and the second source is a Sb or Te source.In other embodiments, the first source is a Sb or Te source, and thesecond source is a Ge source.

For example, in one embodiment, a reaction gas including the compositionof Formula 1 (discussed above) may be supplied into a reaction chamber.At least a first source may also be supplied into the reaction chamber.The reaction gas may be supplied into the reaction chamber aftersupplying of the first source into the reaction chamber is stopped. Inaddition, a second source may be supplied to the reaction chamber,wherein the reaction gas is not supplied to the reaction chamber duringsupplying the second source into the reaction chamber. Furthermore, thesupplying of the first source and the supplying of the second source maybe partially or wholly overlapped. In certain embodiments, supplying ofthe second source occurs after supplying of the first source is stoppedand before supplying of the reaction gas starts. For example, in oneembodiment, during one cycle, a start of supplying the second source mayoccur after, or at the same time as, supplying of the first source isstopped, and an end of supplying the second source may occur before, orat the same time as, supplying of the reaction gas starts. In anotherembodiment, the supplying of the reaction gas may occur after supplyingof the first source is stopped and before supplying the second sourcestarts. For example, in one embodiment, during one cycle, a start ofsupplying the reaction gas may occur after, or at the same time as,supplying of the first source is stopped, and an end of supplying thereaction gas may occur before, or at the same time as, supplying of thesecond source starts. These different examples are shown in FIG. 10,examples (1)-(4).

In other embodiments, a plasma of a reaction gas may be provided to areaction chamber, and a first source and/or a second source may also beprovided to the reaction chamber. One or both of the first source andthe second source may be provided to the reaction chamber as a plasma.The plasma of the reaction gas may be provided to the reaction chamber,for example, by forming the plasma of the reaction gas outside thereaction chamber, and supplying the plasma of the reaction gas into thereaction chamber. Alternatively, the plasma of the reaction gas may beprovided to the reaction chamber, for example, by supplying the reactiongas into the reaction chamber, and forming the plasma of the reactiongas in the reaction chamber. The first or second sources may be providedto the reaction chamber while providing the plasma of the reaction gasto the reaction chamber.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

What is claimed is:
 1. A method of forming a phase change materiallayer, the method comprising: supplying a reaction gas including thecomposition of Formula 1 into a reaction chamber; and supplying at leasta first source which includes Ge(II) into the reaction chamber; whereina start of supplying the reaction gas into the reaction chamber occursafter supplying of the first source into the reaction chamber isstopped;NR₁R₂R₃  Formula 1 wherein R₁, R₂ and R₃ are each independently at leastone selected from the group consisting of H, CH₃, C₂H₅, C₃H₇, C₄H₉,Si(CH₃)₃, NH₂, NH(CH₃), N(CH₃)₂, NH(C₂H₅) and N(C₂H₅)₂.
 2. The methodaccording to claim 1, further comprising: supplying a second sourcewherein the reaction gas is not supplied to the reaction chamber duringsupplying the second source into the reaction chamber.
 3. The methodaccording to claim 2, wherein supplying of the first source andsupplying of the second source are at least partially overlapped.
 4. Themethod according to claim 2, wherein supplying of the second sourceoccurs after supplying of the first source is stopped and beforesupplying of the reaction gas starts.
 5. The method according to claim2, wherein supplying the reaction gas occurs after supplying of thefirst source is stopped and before supplying the second source starts.6. The method according to claim 1, wherein the first source comprisesat least one selected from the group consisting of amide ligand, aphosphanido ligand, an alkoxide ligand and a thiolate ligand.
 7. Themethod according to claim 6, wherein the first source includes thecomposition of at least one of Formulae 2 to 4:R₁R₂X₁—Ge—X₂R₃R₄  Formula 2 wherein X₁ and X₂ are each independently atleast one of N and P, and wherein R₁, R₂, R₃ and R₄ are eachindependently at least one selected from the group consisting of (a) ahydrogen atom, (b) a C₁-C₁₀ alkyl group, (c) a C₁-C₁₀ alkyl group, whereCH₃ is substituted with an imine group, an amine group, an alkoxy groupor a ketone group, (d) a C₁-C₁₀ alkyl group, where CH₃ is substitutedwith an imine group, an amine group, an alkoxy group or a ketone group,and where N of the imine group, N of the amine group, O of the alkoxygroup or O of the ketone group is coordinated with Ge, (d) a C₂-C₁₂olefinic group, (f) a C₃-C₁₂ olefinic group, where CH₃ is substitutedwith an imine group, an amine group, an alkoxy group or a ketone group,(g) a C₃-C₁₂ olefinic group, where CH₃ is substituted with an iminegroup, an amine group, an alkoxy group or a ketone group, where N of theimine group, N of the amine group, O of the alkoxy group or O of theketone group is coordinated with Ge, (h) a C₂-C₁₃ acetylenic group, (i)an allenic group (CHCCH₂), (j) a cyano group (CN), (k) a NCX group,where X is O, S, Se or Te, (l) an azide ligand (N₃), (m) an amide ligand(NR₅R₆, where R₅ and R₆ are each independently a hydrogen atom, a C₁-C₁₀alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenic group or anallenic group), (n) SiR₇R₈R₉, where R₇, R₈ and R₉ are each independentlya hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃acetylenic group or an allenic group, and wherein the representation ofFormula 2 includes non-ring systems and ring systems in which at leasttwo of the R₁, R₂, R₃ and R₄ are chemically linked;R₁Y₁—Ge—Y₂R₂  Formula 3 wherein Y₁ and Y₂ are each independently atleast one of O and S, wherein R₁ and R₂ are each independently at leastone selected from the group consisting of (a) a hydrogen atom, (b) aC₁-C₁₀ alkyl group, (c) a C₁-C₁₀ alkyl group, where CH₃ is substitutedwith an imine group, an amine group, an alkoxy group or a ketone group,(d) a C₁-C₁₀ alkyl group, where CH₃ is substituted with an imine group,an amine group, an alkoxy group or a ketone group, and where N of theimine group, N of the amine group, O of the alkoxy group or O of theketone group is coordinated with Ge, (e) a C₂-C₁₂ olefinic group, (f) aC₃-C₁₂ olefinic group, where CH₃ is substituted with an imine group, anamine group, an alkoxy group or a ketone group, (g) a C₃-C₁₂ olefinicgroup, where CH₃ is substituted with an imine group, an amine group, analkoxy group or a ketone group, and where N of the imine group, N of theamine group, O of the alkoxy group or O of the ketone group iscoordinated with Ge, (h) a C₂-C₁₃ acetylenic group, (i) an allenic group(CHCCH₂), (j) a cyano group (CN), (k) a NCX group, where X is O, S, Seor Te, (l) an azide ligand (N₃), (m) an amide ligand (NR₃R₄, where R₃and R₄ are each independently a hydrogen atom, a C₁-C₁₀ alkyl group, aC₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenic group or an allenic group),(n) SiR₅R₆R₇, where R₅, R₆ and R₇ are each independently at least one ofa hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃acetylenic group or an allenic group, and wherein the representation ofFormula 3 includes non-ring systems and ring systems in which R₁ and R₂are chemically linked;R₁R₂X—Ge—YR₃  Formula 4 wherein X is at least one of N and P, and Y isat least one of O and S, wherein R₁, R₂ and R₃ are each independently atleast one selected from the group consisting of (a) a hydrogen atom, (b)a C₁-C₁₀ alkyl group, (c) a C₁-C₁₀ alkyl group, where CH₃ is substitutedwith an imine group, an amine group, an alkoxy group or a ketone group,(d) a C₁-C₁₀ alkyl group, where CH₃ is substituted with an imine group,an amine group, an alkoxy group or a ketone group, and where N of theimine group, N of the amine group, O of the alkoxy group or O of theketone group is coordinated with Ge, (d) a C₂-C₁₂ olefinic group, (f) aC₃-C₁₂ olefinic group, where CH₃ is substituted with an imine group, anamine group, an alkoxy group or a ketone group, and where N of the iminegroup, N of the amine group, O of the alkoxy group or O of the ketonegroup is coordinated with Ge, (g) a C₂-C₁₃ acetylenic group, (h) anallenic group (CHCCH₂), (i) a cyano group (CN), (j) a NCX group, where Xis O, S, Se or Te, (k) an azide ligand (N₃), (l) an amide ligand (NR₄R₅,where R₄ and R₅ are each independently a hydrogen atom, a C₁-C₁₀ alkylgroup, a C₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenic group or an allenicgroup), (m) SiR₆R₇R₈, where R₆, R₇ and R₈ are each independently ahydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃acetylenic group or an allenic group, and wherein the representation ofFormula 4 includes non-ring systems and ring systems in which at leasttwo of R₁, R₂ and R₃ are chemically linked.
 8. The method according toclaim 6, wherein the first source includes the composition of at leastone of Formulae 5 to 17:

wherein X₁ and X₂ are each independently one of N and P, and wherein R₁,R₂, R₃ and R₄ are each independently one selected from the groupconsisting of a hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinicgroup, a C₂-C₁₃ acetylenic group and an allenic group;

wherein X₁ and X₂ are each independently one of N and P, and wherein R₁and R₂ are each independently one selected from the group consisting ofa hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃acetylenic group and an allenic group;

wherein X₁, X₂, X₃ and X₄ are each independently one of N and P, andwherein R₁, R₂, R₃, R₄, R₅ and R₆ are each independently one selectedfrom the group consisting of a hydrogen atom, a C₁-C₁₀ alkyl group, aC₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenic group and an allenic group;

wherein X₁ and X₂ are each independently one of N and P, wherein Y₁ andY₂ are each independently one of O and S, and wherein R₁, R₂, R₃, R₄,R₅, R₆, R₇ and R₈ are each independently one selected from the groupconsisting of a hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinicgroup, a C₂-C₁₃ acetylenic group and an allenic group;

wherein X₁, X₂, X₃ and X₄ are each independently one of N and P, andwherein R₁, R₂, R₃, R₄, R₅, R₆, R₇, R₈, R₉ and R₁₀ are eachindependently one selected from the group consisting of a hydrogen atom,a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenic groupand an allenic group;

wherein X₁, X₂, X₃ and X₄ are each independently one of N and P, andwherein R₁, R₂, R₃, R₄, R₅ and R₆ are each independently one selectedfrom the group consisting of a hydrogen atom, a C₁-C₁₀ alkyl group, aC₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenic group and an allenic group;

wherein X₁ and X₂ are each independently one of N and P, wherein Y₁ andY₂ are each independently one of O and S, and wherein R₁, R₂, R₃ and R₄are each independently one selected from the group consisting of ahydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃acetylenic group and an allenic group;

wherein Y₁ and Y₂ are each independently one of O and S, and wherein R₁and R₂ are each independently one selected from the group consisting ofa hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃acetylenic group and an allenic group;

wherein Y₁ and Y₂ are each independently one of O and S, and wherein R₁and R₂ are each independently one selected from the group consisting ofa hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃acetylenic group and an allenic group;

wherein Y₁, Y₂, Y₃ and Y₄ are each independently one of O and S, andwherein R₁, R₂, R₃, R₄, R₅ and R₆ are each independently one selectedfrom the group consisting of a hydrogen atom, a C₁-C₁₀ alkyl group, aC₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenic group and an allenic group;

wherein X₁ and X₂ are each independently one of N and P, wherein Y₁ andY₂ are each independently one of O and S, and wherein R₁, R₂, R₃ and R₄are each independently one selected from the group consisting of ahydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃acetylenic group and an allenic group;

wherein Y₁, Y₂, Y₃ and Y₄ are each independently one of O and S, andwherein R₁ and R₂ are each independently one selected from the groupconsisting of a hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinicgroup, a C₂-C₁₃ acetylenic group and an allenic group; and

wherein X is one of N and P, wherein Y is one of O and S, and whereinR₁, R₂ and R₃ are each independently one selected from the groupconsisting of a hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinicgroup, a C₂-C₁₃ acetylenic group and an allenic group.
 9. A method offabricating a phase change material layer, the method comprising:providing a plasma of a reaction gas including the composition ofFormula 1 to a reaction chamber; and providing at least a first sourcewhich includes Ge(II) to the reaction chamber; wherein the first sourceis provided to the reaction chamber while providing a plasma of thereaction gas to the reaction chamber;NR1R2R3  Formula 1 wherein R1, R2 and R3 are each independently at leastone selected from the group consisting of H, CH3, C2H5, C3H7, C4H9,Si(CH3)3, NH2, NH(CH3), N(CH3)2, NH(C2H5) and N(C2H5)2.
 10. The methodaccording to claim 9, wherein the first source is provided to thereaction chamber as a plasma.
 11. The method according to claim 9,further comprising: providing a second source to the reaction chamber.12. The method according to claim 11, wherein the second source isprovided to the reaction chamber as a plasma.
 13. The method accordingto claim 9, wherein providing the plasma of the reaction gas to thereaction chamber comprises: forming the plasma of the reaction gasoutside the reaction chamber; and supplying the plasma of the reactiongas into the reaction chamber.
 14. The method according to claim 9,wherein providing the plasma of the reaction gas comprises: supplyingthe reaction gas into the reaction chamber; and forming the plasma ofthe reaction gas in the reaction chamber.
 15. The method according toclaim 9, wherein the first source includes the composition of at leastone of Formulae 2 to 4:R₁R₂X₁—Ge—X₂R₃R₄  Formula 2 wherein X₁ and X₂ are each independently atleast one of N and P, and wherein R₁, R₂, R₃ and R₄ are eachindependently at least one selected from the group consisting of (a) ahydrogen atom, (b) a C₁-C₁₀ alkyl group, (c) a C₁-C₁₀ alkyl group, whereCH₃ is substituted with an imine group, an amine group, an alkoxy groupor a ketone group, (d) a C₁-C₁₀ alkyl group, where CH₃ is substitutedwith an imine group, an amine group, an alkoxy group or a ketone group,and where N of the imine group, N of the amine group, O of the alkoxygroup or O of the ketone group is coordinated with Ge, (d) a C₂-C₁₂olefinic group, (f) a C₃-C₁₂ olefinic group, where CH₃ is substitutedwith an imine group, an amine group, an alkoxy group or a ketone group,(g) a C₃-C₁₂ olefinic group, where CH₃ is substituted with an iminegroup, an amine group, an alkoxy group or a ketone group, where N of theimine group, N of the amine group, O of the alkoxy group or O of theketone group is coordinated with Ge, (h) a C₂-C₁₃ acetylenic group, (i)an allenic group (CHCCH₂), (j) a cyano group (CN), (k) a NCX group,where X is O, S, Se or Te, (l) an azide ligand (N₃), (m) an amide ligand(NR₅R₆, where R₅ and R₆ are each independently a hydrogen atom, a C₁-C₁₀alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenic group or anallenic group), (n) SiR₇R₈R₉, where R₇, R₈ and R₉ are each independentlya hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃acetylenic group or an allenic group, and wherein the representation ofFormula 2 includes non-ring systems and ring systems in which at leasttwo of the R₁, R₂, R₃ and R₄ are chemically linked;R₁Y₁—Ge—Y₂R₂  Formula 3 wherein Y₁ and Y₂ are each independently atleast one of O and S, wherein R₁ and R₂ are each independently at leastone selected from the group consisting of (a) a hydrogen atom, (b) aC₁-C₁₀ alkyl group, (c) a C₁-C₁₀ alkyl group, where CH₃ is substitutedwith an imine group, an amine group, an alkoxy group or a ketone group,(d) a C₁-C₁₀ alkyl group, where CH₃ is substituted with an imine group,an amine group, an alkoxy group or a ketone group, and where N of theimine group, N of the amine group, O of the alkoxy group or O of theketone group is coordinated with Ge, (e) a C₂-C₁₂ olefinic group, (f) aC₃-C₁₂ olefinic group, where CH₃ is substituted with an imine group, anamine group, an alkoxy group or a ketone group, (g) a C₃-C₁₂ olefinicgroup, where CH₃ is substituted with an imine group, an amine group, analkoxy group or a ketone group, and where N of the imine group, N of theamine group, O of the alkoxy group or O of the ketone group iscoordinated with Ge, (h) a C₂-C₁₃ acetylenic group, (i) an allenic group(CHCCH₂), (j) a cyano group (CN), (k) a NCX group, where X is O, S, Seor Te, (l) an azide ligand (N₃), (m) an amide ligand (NR₃R₄, where R₃and R₄ are each independently a hydrogen atom, a C₁-C₁₀ alkyl group, aC₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenic group or an allenic group),(n) SiR₅R₆R₇, where R₅, R₆ and R₇ are each independently at least one ofa hydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃acetylenic group or an allenic group, and wherein the representation ofFormula 3 includes non-ring systems and ring systems in which R₁ and R₂are chemically linked;R₁R₂X—Ge—YR₃  Formula 4 wherein X is at least one of N and P, and Y isat least one of O and S, wherein R₁, R₂ and R₃ are each independently atleast one selected from the group consisting of (a) a hydrogen atom, (b)a C₁-C₁₀ alkyl group, (c) a C₁-C₁₀ alkyl group, where CH₃ is substitutedwith an imine group, an amine group, an alkoxy group or a ketone group,(d) a C₁-C₁₀ alkyl group, where CH₃ is substituted with an imine group,an amine group, an alkoxy group or a ketone group, and where N of theimine group, N of the amine group, O of the alkoxy group or O of theketone group is coordinated with Ge, (d) a C₂-C₁₂ olefinic group, (f) aC₃-C₁₂ olefinic group, where CH₃ is substituted with an imine group, anamine group, an alkoxy group or a ketone group, and where N of the iminegroup, N of the amine group, O of the alkoxy group or O of the ketonegroup is coordinated with Ge, (g) a C₂-C₁₃ acetylenic group, (h) anallenic group (CHCCH₂), (i) a cyano group (CN), (j) a NCX group, where Xis O, S, Se or Te, (k) an azide ligand (N₃), (l) an amide ligand (NR₄R₅,where R₄ and R₅ are each independently a hydrogen atom, a C₁-C₁₀ alkylgroup, a C₂-C₁₂ olefinic group, a C₂-C₁₃ acetylenic group or an allenicgroup), (m) SiR₆R₇R₈, where R₆, R₇ and R₈ are each independently ahydrogen atom, a C₁-C₁₀ alkyl group, a C₂-C₁₂ olefinic group, a C₂-C₁₃acetylenic group or an allenic group, and wherein the representation ofFormula 4 includes non-ring systems and ring systems in which at leasttwo of R₁, R₂ and R₃ are chemically linked.